The goal of this study is to understand how neural circuitry in the brain generates the eye movements required to maintain gaze stability. This problem is of clinical importance since loss of gaze stability severely degrades visual acuity. Since the vestibuloocular reflex serves as a model for motor system function in general, this project will also help to increase understanding of other critical motor processes such as limb movements, postural control and locomotion. A powerful new approach involving analysis of motor function in 3 dimensions will be used to examine the properties of the vestibuloocular reflex (VOR) and optokinetic reflex and of the neural pathways that mediate them. These reflexes will be studied during rotation of an animal or of its visual surround in many planes in 3-dimensional space. Spatial and dynamic properties of the VOR will be determined by recording from the six eye muscles during such rotations. Then activity of single neurons with inputs and projections identified electrophysiologically will be recorded to determine how the brain transforms vestibular input into muscle output. When normal 3-dimensional vestibuloocular behavior has been characterized, plastic changes in the VOR that follow vestibular lesions or visuo-vestibular training will be studied at reflex and neural levels. The goal is to understand how the nervous system compensates for lesions that affect vestibuloocular function, a problem of great importance in the care and rehabilitation of patients suffering from stroke, head trauma or other neurological problems. These experiments should also bring us closer to understanding the neuronal mechanisms underlying motor learning.